Synthetic grass fields (or artificial turf) have been used for years to provide a surface that simulates natural grass. These synthetic grass fields have many benefits over natural grass and, in addition, can be installed and used in places that do not allow for natural grass fields.
One type of synthetic grass field that is commonly used is an infilled synthetic grass field. The infilled synthetic grass field includes a plurality of fibers (also referred to as filaments or ribbons), wherein the fibers are operatively attached to a backing member. Typically the fibers are tufted through the backing member. In most instances, once the backing member (with fibers) is installed on a substrate or other supporting surface, an infill material (typically, rubber, sand or a mixture thereof) is installed to support the fibers in an upright position.
The fibers must be durable enough to withstand the impact and forces imparted thereon during the use of the synthetic grass field. The fibers should also have sufficient structural strength so that at least the exposed portions of some of the fibers can extend above the infill (as opposed to laying flat thereon).
For a synthetic grass field located outside, the fibers should also be able to withstand the forces of nature that act thereon (i.e., have sufficient “weatherability”).
In addition to having sufficient weatherability and being sufficiently durable, the fibers should not be too abrasive that it could injure users of the synthetic grass field.
Furthermore, it is usually desirable that the fibers simulate the look of natural grass.
Conventional fibers utilize various shapes and geometries to provide for these and other considerations.
For example, U.S. Pat. No. 6,491,991 discloses a spinneret used to make fibers for artificial turf. The fibers have a series of increasingly larger bulbs (as the bulbs approach the middle). While presumably effective for its intended purpose, such a fiber is believed to be prone to fray, as the intersections where the bulbs meet form weak points. Moreover, the convex bulbs are believed to transfer the physical forces to these intersection points, which add to the proneness of such a fiber to fray.
Japanese Patent Application No. JP9111532A discloses another fiber, similar to those in the '991 patent, comprising a series of bulbs. Again, it is believed that such a fiber is more prone to fraying along the intersection points between bulbs.
EP 1 950 350 A1 discloses various fibers, some of which have bulbs at the center and on the ends. These fibers have stress points at the point the bulbs are connected to the fiber. As a result, these types of fibers have a tendency to fray or split along these stress points.
A further fiber is disclosed in WO 2011/006878 which is a curved or “sickle-shaped” cross section. The fiber also includes a plurality of ridges arranged along the longitudinal direction of the grass yarn. Such a fiber has a series of flat sections between the ridges, which is believed to make the fiber appear less like natural grass. Moreover, since the ridges protrude out of the body of the fiber, it is believed that they increase the thickness of the fiber which can make the fiber too stiff and not desirable for certain applications.
The present invention is directed to providing a fiber having a shape and geometry that attempts to adequately balance each of these considerations.